Project Summary/Abstract The main objective of the project is to investigate the effect of compositional differences in topical products on the physical, structural and functional properties. The other objective is to It develop additional, product specific characterization tools and methodologies to explore the structural and thermodynamic changes that occur during metamorphosis of topical products. As the risk of failure modes for BE is relatively higher in compositionally different products, there is need to systematically investigate the potential failure modes and approaches to mitigate them.We propose three specific aims in this project. In aim 1 we propose to investigate the influence of systematic compositional alterations, on the microstructural characteristics, metamorphosis, and performance attributes of topical products. To develop a theoretical framework to describe the fundamental factors that govern topical dosage form performance. Different case studies will be formulated to consider various products with different levels of complexities. Different product types, such as solutions, colloidal products, gels, suspensions, creams, microemulsions, foams, and nanotechnology products, will be considered. In each case, a sequence of products will be prepared by systematic alteration in the product composition. Some of the ways (not limited to) of changing the composition would include: a) changing the amount of one or more ingredients or b) by replacing one or more of the ingredients with an ingredient that is of same chemical class/ pharmaceutical category and c) by using an ingredient of different grades/quality/source. The thermodynamical characterization would be of major emphasis in the proposed experiments. Finally, a theoretical framework to describe the fundamental principles that govern the performance of topical products will be developed. In aim 2, we propose to develop novel tools and methods to characterize the microstructural attributes of topical products. One of the objectives is to modify the standard conventional methods and validate them for application across broad categories of topical products. Novel methods will also be developed to understand the differences in microstructure and thermodynamic characteristic between products of different compositions. In aim 3, To identify the potential failure modes in nonQ1 and/or non-Q2 products and to investigate the approaches to mitigate the risk. Potential failure modes would be assessed in individual case studies, proposed in this project, and potential approaches to mitigate the risk would be explored as well. The successful completion of the proposed studies, is believed to generate information that would be used to develop a theoretical framework to describe the fundamental principles that govern the performance of topical products.